Epitaxial growth of silicon carbide (SiC) is traditionally conducted by chemical vapor deposition (CVD) with silane and propane precursors at temperatures in excess of 1500° C. Other sources were occasionally used instead of silane and propane including single-precursors containing both silicon and carbon components or precursors containing chlorine (Cl) and other molecules. See Powell, J. A. and Will, H. A., “Epitaxial Growth of 6H SiC in the Tempetature Range 1320-1390° C.,” J. Appl. Phys., Vol. 44, No. 11, pp. 5177-5178, 1973; and Nishino, S. et al., “Epitaxial Growth of SiC on a α-SiC Using Si2Cl6+C3H8+H2 System,” Mater. Sci. For., Vols. 264-268, pp. 139-142, 1998. Epitaxial growth with the traditional growth precursor gasses at temperatures below 1400° C. was also attempted in the research environment with limited success. See Yamashita, A. et al., “Homoepitaxial Chemical Vapor Deposition of 6H—SiC at Low Temperatures on {0114} Substrates,” Jpn. J. Appl. Phys., Vol. 31, pp. 3655-3661, 1992.
Elevated temperatures are required to provide: (1) efficient decomposition of the gaseous precursors to form reaction products required for epitaxial growth; (2) suppressed formation or enhanced dissociation of silicon clusters that may form in the reactor; and (3) suppressed two-dimensional and three-dimensional nucleation at the surface in favor of desirable step-flow growth mechanism. If conducted at reduced temperatures (below 1400-1450° C.), the epitaxial growth on SiC surface of arbitrary orientation may result in polytype inclusions, degraded morphology, and even in polycrystalline material. Only growth on selected surface orientations was reported to produce promising growth morphology at reduced temperatures. See Powell, J. A. and Will, H. A., “Epitaxial Growth of 6H SiC in the Temperature Range 1320-1390° C.,” J. Appl. Phys., Vol. 44, No. 11, pp. 5177-5178, 1973; and Nishino, S. et al., “Epitax Growth of SiC on a α-SiC Using Si2Cl6+C3H8+H2 System,” Mater. Sci. For., Vols. 264-268, pp. 139-142, 1998; Yamashita, A. et al., “Homoepitaxial Chemical Vapor Deposition of 6H—SiC at Low Temperatures on {0114} Substrates,” Jpn. J. Appl. Phys., Vol. 31, pp. 3655-3661, 1992. Also, most of the low-temperature homoepitaxial growth experiments were focused on 6H—SiC polytype.
For these reasons, temperatures in excess of 1450° C. are normally used for epitaxial growth of 4H- and 6H—SiC polytypes on 4H- and 6H—SiC substrates respectively. 3C—SiC polytype is grown heteroepitaxially on silicon substrates at temperatures below 1300° C., however, attempts to reduce growth temperatures normally result in epitaxial layer quality degradation. On the other hand, growth at high temperatures introduces a number of complications. First, there are important cost issues including degradation of the reactor hardware—e.g., quartz, susceptor, substrate holder, etc. Second, high-temperature growth may complicate control of the incorporation of dopants and other impurities in the grown epilayer. Third, high temperatures may increase lattice defect generation, surface roughness and surface morphology degradation. In addition, high-temperature growth on lower off-angle and on-axis substrates results in bad quality materials.
Addition of halogenated precursors and other additional components (including HCl, chlorinated sources of silane, etc.) was proposed and attempted to improve surface and gas-phase reaction mechanisms (see Nishino, S. et al., “Epitaxial Growth of SiC on a α-SiC Using Si2Cl6+C3H8+H2 System,” Mater. Sci. For., Vols. 264-268, pp. 139-142, Xie, Z. Y. et al., “Polytype Controlled SiC Epitaxy on On-axis 6H—SiC(0001) by Adding HCl during Growth,” Electrochemical and Solid-State Letters, 3(8), pp. 381-384, 2000; and Koshka, Y. et al., “Homoepitaxial Growth of 4H—SiC Using CH3Cl Carbon Precursor,” Mater. Sci. For., Vols. 483-485, pp. 81-84, 2005) at regular growth temperature (i.e., in excess of 1450-1500° C.). However, it has not received any significant commercial use and has not been applied to achieve lower-temperature homoepitaxial growth.
Use of CH3Cl in epitaxial growth of SiC has been reported for SiC heteroepitaxial growth (i.e., 3C—SiC on silicon). See Ikoma, K. et al., “Heteroepitaxial Growth of β-SiC on Si (111) by CVD Using a CH3Cl—SiH4—H2 Gas System,” J. Electrochem. Soc., Vol. 138, No. 10, pp. 3028-3031, 1991. However, control of the of the gas-phase interaction involving halogenated carbon precursors was not disclosed. Therefore, since the gas-phase interaction constituting the nature of the present invention was not disclosed and no significant benefits of using CH3Cl growth precursor were realized, there has been no continuation of work with halogenated carbon precursors.
For the homoepitaxial growth of SiC (4H—SiC epitaxial layer on 4H—SiC substrates or 6H—SiC epitaxial layer on 6H—SiC substrates), no halogenated carbon precursors had ever been used prior to our invention. More importantly, without the invention of the new mechanism of the gas-phase interaction involving halogenated carbon precursors, a straightforward attempt to use halogenated carbon precursor would not provide any of the benefits that are provided by our invention.